In underground mining operations in which a blasting technique is used for shattering and breaking out an ore body, the blast holes have to be drilled in a stope face, for example, in a predetermined pattern.
Current practice for drilling with a drill rig is to employ hydraulic drills using hydraulic motors powered by an hydraulic power pack in turn energised by an electrical power supply. Not only is the power pack extremely heavy, cumbersome and difficult to move around a stope, and in particular from one stope to the next, but the current form of drill rig is also regarded by applicant as being unsatisfactory.
A hand held water driven drill will typically comprise a drill supported, in articulated manner, at the upper end of a generally inclined and manually manipulated thrust leg which is hydraulically and telescopically extensible with a grip-affording foot at its lower end.
In order to use one of these drills, two persons are required, one in order to locate the end of the drill relative to the rock face until it becomes collared, and the other to manipulate the drill boom and thrust leg so that the drill adopts the correct orientation and, in particular, axial direction.
The pattern of holes to be drilled may be of many different types, but a typical one would include three vertically spaced rows of equally spaced holes with the holes of the middle row being offset from those in the upper and lower rows by approximately one half of the distance between any two holes in a row. Some holes need to be drilled rather close to the extremities of the stope and drilling these holes, in particular, is extremely difficult, particularly with regard to collaring the drill.
It is also extremely difficult to ensure that all the adjacent holes in a row are parallel to each other due to the adjustments available on each boom.
The current drill rigs for use in stopes generally comprise one or two booms which are hydraulically adjusted to the correct position. The associated electrohydraulic power pack is generally an integral part of the rig and must move with it. The boom is generally telescopic so that once it is in position it must be moved forward to butt up against the rock face for support before drilling takes place. Because the booms are fully adjustable, the rock face must be marked so that the position of each hole is indicated before the time. The direction and dip of the hole must also be indicated because of the infinite adjustment and thus operator discretion.
Furthermore, the present mechanism for transmitting movement from the hydraulic piston and cylinder to the drill unit itself to move same along the boom, is not entirely satisfactory. In the existing arrangement a piston and cylinder is located beneath, or at least offset from, but parallel to, the path of movement of the drill unit and movement is transferred to the drill unit by way of a cable or chain passing over a pulley at the end of the boom remote from the rock face being drilled.